1. Field
The disclosure relates to the manufacture of tires and focuses more specifically on the processing of the reinforcing plies produced from textile threads.
2. Description of Related Art
These plies are formed by sections of threads embedded in rubber and are arranged at a given angle in relation to the circumferential direction of the tire.
In a known manner, the manufacture of the reinforcing plies takes place on the basis of plies of threads, known as straight-thread plies, in which the continuous threads are arranged side by side, according to a given pitch, in a direction parallel to the longitudinal direction of the ply. The threads of the ply are embedded in the rubber, for example by means of a calender.
The threads of the straight-thread ply may be subjected to pre-treatment in order to favour the adhesion of the rubber to the thread.
In addition, in a routine manner, these straight-thread plies include sections of threads, referred to as weft threads, arranged in the direction perpendicular to the longitudinal direction of the straight-thread ply, of which the threads may be considered as warp threads. The purpose of the weft threads is to maintain the threads of the straight-thread ply in position during the handling operations of said plies.
It can be appreciated, however, that the presence of the weft may prove to be inconvenient during subsequent operations in the manufacture of the tire. In effect, when these threads are present in a ply intended to form the carcass-reinforcing ply, they may cause irregularities in the spacing of the reinforcing threads at the level of the crown portion. This can be explained by the fact that the weft threads act against an increase in the spacing pitch of the reinforcing threads in this zone in the course of the conformation operation, the purpose of which is to transform the tire blank from a generally cylindrical shape into a toroidal shape.
The manufacturers are also committed to reducing this disadvantage by fragmenting and/or by withdrawing the weft threads during a stage preceding the embedding of the reinforcing threads in their rubber matrix.
Devices intended for this purpose have been developed by the industry. Thus, publication JP7-34379 describes a system of rotating knives capable of cutting the wefts into sections of a given size, interacting with claws mounted on a rotating disc and intended to hook onto and to extract the sections of wefts. Publication JP5-200910 describes a similar system in which the claws may be mounted on an axis executing a rectilinear movement.
One or a plurality of these devices are thus arranged with regular spacing in the direction transversal to the direction of the straight-thread ply downstream of cutting means capable of dissecting the weft threads in order to extract the wefts prior to the calendering operation, in the course of which the reinforcing threads are embedded in rubber.
It should be noted, however, that, although these devices permit the removal of the majority of the sections of weft, some sections of weft will remain intertwined in an irregular manner with the reinforcing threads. In addition, on emerging from the calendering operation, these weft residues constitute local thickenings and aggregates with the potential to weaken the bridges of rubber formed between the reinforcing threads.